The propensity score \(p_{u,i}\)  blackis defined as the tendency of the deployed model to expose item \(i\)  to user \(u\)  (Definition ).
blackSince it is not blackrealistic for the deployed model to expose each and every item to the user, we have to estimate blackthe propensity scores \(p_{u,i}\)  for various user and item pairs.
Yang et al. [1]} proposed a simple method to estimate blackthe propensity scores based on the following simplified assumption:
